The complex nature of bass frequencies

[Guest MoJo]

Last night's rehearsal started like any other. I plugged into the bass rig provided in room 3, a Behringer HA3000 through a Peavey 410TVX. I fiddled with the parametric eq until I achieved an approximation of 'my sound' and the rehearsal began.

Now I'd heard previously about bass frequencies hanging around in corners like a bunch of chavs with a spiff and also seen 'corner bass traps' advertised in the Studio Spares catalogue but, half way through the rehearsal, the vocalist vacates his spot in the corner to my right and drags his mic and stand to the centre of the wall opposite the drums. Being the wandering minstrel that I am, I moved over into the vacated corner and [b] [/b]. The effect was immense. No more volume from the bass but so much more clean low end. Stepping forward four feet defeated the effect. I got both the guitarist and the drummer to experience the effect with similar huge grin results. Simply dialling in more low end on the amp just made the cab sound boomy and wooly not like the sound in the corner.

This just demonstrates to me the complex nature of bass frequencies. Even with a cab with excellent off-axis response, there's always going to be someone in your audience either sat in a bass trap (they'll be the one telling you your bass is too loud at half time) or in an area where out-of-phase reflections cancel out your cabs output causing a bass void. The only way forward is for the audience to all wear headphones .

[leftybassman392]

[quote name='bassman2790' post='547295' date='Jul 22 2009, 08:45 AM']Last night's rehearsal started like any other. I plugged into the bass rig provided in room 3, a Behringer HA3000 through a Peavey 410TVX. I fiddled with the parametric eq until I achieved an approximation of 'my sound' and the rehearsal began.

Now I'd heard previously about bass frequencies hanging around in corners like a bunch of chavs with a spiff and also seen 'corner bass traps' advertised in the Studio Spares catalogue but, half way through the rehearsal, the vocalist vacates his spot in the corner to my right and drags his mic and stand to the centre of the wall opposite the drums. Being the wandering minstrel that I am, I moved over into the vacated corner and [b] [/b]. The effect was immense. No more volume from the bass but so much more clean low end. Stepping forward four feet defeated the effect. I got both the guitarist and the drummer to experience the effect with similar huge grin results. Simply dialling in more low end on the amp just made the cab sound boomy and wooly not like the sound in the corner.

This just demonstrates to me the complex nature of bass frequencies. Even with a cab with excellent off-axis response, there's always going to be someone in your audience either sat in a bass trap (they'll be the one telling you your bass is too loud at half time) or in an area where out-of-phase reflections cancel out your cabs output causing a bass void. The only way forward is for the audience to all wear headphones .[/quote]

It's the same idea as the one used by HiFi speaker designers - placing the speaker cabinet close to the back wall reinforces the bass notes - most designers of small speakers do it, and often give very precise distances for best results. In a corner you have two walls - multiplies the effect. In fact, the PJB Flightcase bass amp comes with a strong recommendation that you place it on the floor (despite its small size), and if possible close to a rear wall - the user manual actually goes into quite a lot of detail about how it works. Recommended reading (you can download a PDF copy from the PJB website).

[High score]

[quote name='bassman2790' post='547295' date='Jul 22 2009, 08:45 AM']Last night's rehearsal started like any other. I plugged into the bass rig provided in room 3, a Behringer HA3000 through a Peavey 410TVX. I fiddled with the parametric eq until I achieved an approximation of 'my sound' and the rehearsal began.

Now I'd heard previously about bass frequencies hanging around in corners like a bunch of chavs with a spiff and also seen 'corner bass traps' advertised in the Studio Spares catalogue but, half way through the rehearsal, the vocalist vacates his spot in the corner to my right and drags his mic and stand to the centre of the wall opposite the drums. Being the wandering minstrel that I am, I moved over into the vacated corner and [b] [/b]. The effect was immense. No more volume from the bass but so much more clean low end. Stepping forward four feet defeated the effect. I got both the guitarist and the drummer to experience the effect with similar huge grin results. Simply dialling in more low end on the amp just made the cab sound boomy and wooly not like the sound in the corner.

This just demonstrates to me the complex nature of bass frequencies. Even with a cab with excellent off-axis response, there's always going to be someone in your audience either sat in a bass trap (they'll be the one telling you your bass is too loud at half time) or in an area where out-of-phase reflections cancel out your cabs output causing a bass void. The only way forward is for the audience to all wear headphones .[/quote]

+1
totally right but unfortunately we don't live in a hifi designed world and instead gig in pubs that are designed for kids playrooms instead. This means there is invariably a trade off due to sound reflections and available 'postage stamp' space you are given for setup!! At least you have recognised that increasing the bass level (vol and/or eq) may give you a woolly effect. As well as exploring sweet spots with levels, try exploring the eq range as well and perhaps cutting the low end slightly and increasing mids - often less is more. You should also be aware that finding sweet spots in practice will be different from venue to venue but now you are aware of it. This is why a soundman will commonly be placed where he/she is but they are also aware that it is not 100% in all corners of the room.

Enjoy exploring the sounds your gear gives though - lots of bands don't............

[alexclaber]

This is a standing wave phenomenon, so you get high pressure in the nodes at the reflection points. Although you can't escape it you can at least try to minimise cancellation nulls by correct cab positioning - extra bottom isn't going to hurt anyone or mess up the mix much, but no bottom really will spoil the vibe. A cab with good midrange response, especially off-axis, will suffer less from low frequency response variations round the room because so much of the tone is in the mids, just as a really good small hi-fi speaker is less likely to need a subwoofer to sound good than a cheaper but equally bassy small speaker.

Alex

[Guest MoJo]

[quote name='leftybassman392' post='547308' date='Jul 22 2009, 09:02 AM']It's the same idea as the one used by HiFi speaker designers - placing the speaker cabinet close to the back wall reinforces the bass notes - most designers of small speakers do it, and often give very precise distances for best results. In a corner you have two walls - multiplies the effect. In fact, the PJB Flightcase bass amp comes with a strong recommendation that you place it on the floor (despite its small size), and if possible close to a rear wall - the user manual actually goes into quite a lot of detail about how it works. Recommended reading (you can download a PDF copy from the PJB website).[/quote]

Will do, thanks

[mrcrow]

used to be better bass with the cab/speaker facing the longest dimension of the room

imagine me when i played in a sports hall with the roof about 30 high...and all the walls solid plastering

clank and clank